Metzger David C H, Hemmer-Hansen Jakob, Schulte Patricia M
Department of Zoology, 6270 University Blvd., University of British Columbia, Vancouver, BC V6T 1Z4, Canada.
Section for Marine Living Resources, National Institute of Aquatic Resources, Technical University of Denmark, Vejlsøvej 39, 8600 Silkeborg, Denmark.
Comp Biochem Physiol Part D Genomics Proteomics. 2016 Jun;18:10-20. doi: 10.1016/j.cbd.2016.01.007. Epub 2016 Jan 26.
The cytosolic 70KDa heat shock proteins (Hsp70s) are widely used as biomarkers of environmental stress in ecological and toxicological studies in fish. Here we analyze teleost genome sequences to show that two genes encoding inducible hsp70s (hsp70-1 and hsp70-2) are likely present in all teleost fish. Phylogenetic and synteny analyses indicate that hsp70-1 and hsp70-2 are distinct paralogs that originated prior to the diversification of the teleosts. The promoters of both genes contain a TATA box and conserved heat shock elements (HSEs), but unlike mammalian HSP70s, both genes contain an intron in the 5' UTR. The hsp70-2 gene has undergone tandem duplication in several species. In addition, many other teleost genome assemblies have multiple copies of hsp70-2 present on separate, small, genomic scaffolds. To verify that these represent poorly assembled tandem duplicates, we cloned the genomic region surrounding hsp70-2 in Fundulus heteroclitus and showed that the hsp70-2 gene copies that are on separate scaffolds in the genome assembly are arranged as tandem duplicates. Real-time quantitative PCR of F. heteroclitus genomic DNA indicates that four copies of the hsp70-2 gene are likely present in the F. heteroclitus genome. Comparison of expression patterns in F. heteroclitus and Gasterosteus aculeatus demonstrates that hsp70-2 has a higher fold increase than hsp70-1 following heat shock in gill but not in muscle tissue, revealing a conserved difference in expression patterns between isoforms and tissues. These data indicate that ecological and toxicological studies using hsp70 as a biomarker in teleosts should take this complexity into account.
胞质70KDa热休克蛋白（Hsp70s）在鱼类生态和毒理学研究中被广泛用作环境应激的生物标志物。在此，我们分析硬骨鱼基因组序列，以表明所有硬骨鱼中可能都存在两个编码诱导型hsp70s的基因（hsp70-1和hsp70-2）。系统发育和共线性分析表明，hsp70-1和hsp70-2是不同的旁系同源基因，起源于硬骨鱼多样化之前。这两个基因的启动子都含有一个TATA盒和保守的热休克元件（HSEs），但与哺乳动物HSP70s不同的是，这两个基因在5'UTR中都含有一个内含子。hsp70-2基因在几个物种中经历了串联重复。此外，许多其他硬骨鱼基因组组装在单独的小基因组支架上有多个hsp70-2拷贝。为了验证这些代表组装不佳的串联重复，我们克隆了异齿底鳉中hsp70-2周围的基因组区域，并表明基因组组装中位于不同支架上的hsp70-2基因拷贝排列为串联重复。对异齿底鳉基因组DNA进行实时定量PCR表明，异齿底鳉基因组中可能存在四个hsp70-2基因拷贝。对异齿底鳉和三刺鱼表达模式的比较表明，热休克后，鳃中hsp70-2的倍数增加高于hsp70-1，但肌肉组织中并非如此，这揭示了异构体和组织之间表达模式的保守差异。这些数据表明，在硬骨鱼中使用hsp70作为生物标志物的生态和毒理学研究应考虑到这种复杂性。
